The present invention relates to a method for manufacturing a rod with an optical thin film, and also relates to a rod block for use in this method.
Conventionally, there has been known a technology for previously forming a filter on an endface of a gradient index rod lens and thereby eliminating problems with alignment of the rod lens and the filter element and making the optical system more compact. For example, refer to Japanese Laid-open Patent Publication No. 54-56851.
Furthermore, Japanese Laid-open Patent Publication No. 2002-255580 discloses a technology for integrating with a resin, such as wax, a plurality of slender rod lens preforms having a predetermined refractive index distribution, and cutting off the rod lens preforms into a predetermined length at one time. After each cut endface of the rod lens preforms is subjected to a polishing process and the like, a desired optical film is formed on each endface of the rod lens preforms.
Further, in Japanese Examined Patent Publication No. 3-14590, there is known a technology in which, prior to the film formation, a resin, such as wax for fixing a plurality of rod lens preforms, is removed to separate the rod lens preforms from one another and the separated rod lens preforms are fixed to a jig piece by piece. The reason for separating the rod lens preforms from one another before the film formation is that in the case of integrating the rod lens preforms with a resin, the resin is melted by heat applied during the film formation, and as a result, the rod lens preforms cannot be integrally held, or there is the possibility that the melted wax flows out onto the surface of the rod lens to inhibit the film formation, or the vaporized wax adsorbs on the rod lens endface to cause deterioration in film quality.
However, as for the removal of resin and separation of the rod lens preforms from one another before the optical film formation, and for the fixing of the separated rod lens preforms to a jig, it takes a lot of time to conduct the preliminary work and a long working time is required.
Furthermore, there is the possibility that due to the preliminary work before the film formation, defects are produced, leading to the reduction of the yield. This is because during the preliminary work, there arise problems in that the individual rod lens preforms contact one another, tweezers or the like for clipping small rod lens preforms come into contact with the rod lens preforms and damage the lenses, or small rod lens preforms scatter in all directions and are lost.